1. Field of the Invention
The present invention relates generally to catheters used in the treatment of patients and, more particularly, to soft over-the-needle intravenous catheters that have been treated to harden the distal end to reduce the risk of vascular trauma to the patient and to minimize discomfort during use.
2. Description of the Related Art
Intravenous catheters are well known in the art and serve the function of withdrawing fluids from, or delivering fluids to, a patient undergoing treatment. Typically, either a through-the-needle or an over-the-needle catheter is inserted percutaneously using an insertion needle. With the former catheter, the insertion needle includes a lumen through which the catheter is inserted. With the latter, the needle is inserted into the lumen within the catheter, whereby the catheter fits snugly around the needle. In either case, after the needle and catheter are inserted into the patient's vascular system, the needle is withdrawn, leaving the catheter in place.
Conventional catheters are made of a relatively hard thermoplastic material, such as polyvinylchloride, Teflon® polyurethane or the like, which provides stiff columnar strength during insertion. While the catheter may exhibit axial flexibility, the stiffness of the catheter walls ensures that the catheter will not collapse and will readily follow the needle into the patient's vascular system. The problem with these relatively hard catheters, however, is that they often cause vascular trauma when in use. For example, when the catheter is inserted into the vascular system, the stiffness of the catheter resists the tendency of the blood flow to move the catheter away from the vessel wall and toward the center of the vessel. As such, as the clinician advances the catheter further into the patient, the distal end of the catheter has a tendency to scrape along the wall of the blood vessel as it bends to conform to the shape of the vessel as will be understood by those of skill in the art. Moreover, where the catheter is fed significantly through the patient's vascular system, the catheter's stiffness leads to uncontrolled contact with the vessel wall at various locations, causing discomfort to the patient.
More recently, there have been efforts to employ a softer catheter, one made with a material that is more resilient and flexible and less resistant to the force of blood flow within the blood vessel. Such catheters are beneficial in that they reduce discomfort to the patient and decrease significantly the potential for damage to the blood vessel walls. A limitation of soft material catheters, however, is that they are more difficult to insert than the relatively hard catheters. Due to the resistance of the patient's skin and muscle tissue during insertion, the distal end of the soft catheter often either rolls up axially away from the distal end and/or wrinkles proximally in an accordion-like fashion. Under those circumstances, the catheter does not effectively enter the vascular system on the first attempt, requiring repeated efforts at reentry, which is discomforting to the patient and frustrating to the clinician.
There is a need, therefore, to overcome the limitation of soft material catheters so that they are more effective yet avoid discomfort to the patient by repeated reentry attempts.